Acoustic curb



A ril 16, 1963 L. J. JENN ETAL ACOUSTIC CURB 3 Sheets-Sheet 1 Filed Nov.7, 1960 INVENTORS. LOUIS J. JENN and y WILLIAM E. MORRISON )(WMWMWJJMdWWAH-ornm .s

A ril 16, 1963 L. J. JENN ETAL ACOUSTIC CURB 3 Sheets-Sheet 2 Filed Nov.7, 1960 mmvrox LOUIS J.JENN and y WILLIAM E. MORRISON XJMMWJMfi/M A Horn5V5 A ril 16, 1963 L. J. JENN ETAL 3, 7

ACOUSTIC CURB Filed Nov. 7, 1960 3 Sheets-Sheet 3 39 k 38 M wamINVENTOR.

\ LOUISJ.JENN and H y WILLIAM E.MORmsou Xmmmz J/aZ/d/M A1 forn gysUnited States Patent Q 3,085,647 ACOUSTIC CURB Louis J. Jenn and WilliamE. Morrison, Indianapolis, Ind.,

assignors to Jenn-Air Products Company, Inc., Indianapolis, Ind., acorporation of Indiana Filed Nov. 7, 1960, Ser. No. 67,837 6 Claims.(Cl. 181-56) This invention relates generally to a sound attenuatordesigned for use primarily with power operated air exhausters. Moreparticularly, the invention relates to a prefabricated acoustic curbdesigned to support a centrifugal roof exhauster, the curb beingconstructed so as to provide maximum sound attenuation with a minimum ofpressure loss or restriction to the flow of air through the curb.

In recent years the problem of reducing the sound level of powerexhausters has received considerable attention from industry at large.With the increasing application of power exhausters to structures suchas libraries, schoolrooms, hospitals, conference rooms, churches,auditoriums and the like, the problem of baffling the sound from theexhausters so that the interior of the room or other structure remainsrelatively quiet, has become increasingly important. Structures havebeen utilized by the inventors herein having a primary, central bafflewhich is disposed axially transverse to the direction of air flowthrough the curb, the baffle extending beyond the boundaries of the airinlet and air outlet openings. Air flowing through the curb is thusforced to take a tortuous path around the baffle and through the airoutlet opening. This structure has proven quite satisfactory for mostapplications, however, in the larger size curb structures, adapted foruse with high capacity systems, the primary baflle extending completelyacross the air flow path obstructs the flow of air through the curb to adegree such that pressure losses through the curb are objectionablylarge. The structure of the present invention overcomes this difficultyfor large size curb structures by providing a bypass opening through theprimary baffle, the bypass opening being preferably centrally locatedand shielded or masked by an auxiliary baffle spaced downstream of thebypass opening and extending transversely across the opening.

The primary object of the present invention is to provide an acousticcurb adapted for large size, high capacity systems where increased airflow path cross section is necessary, the baffle arrangement being suchas to effectively intercept sound from the exhauster without in creasingthe pressure drop across the curb to objectionable values.

A further object of the present invention is to provide an acoustic curbstructure utilizing corner members which function to support the primarybafiie and distribute the weight of the exhauster fan to the fourcorners of the curb structure.

The full nature of the invention will be understood from theaccompanying drawings and the following description and the claims.

FIG. 1 is a perspective view of the structure of the present inventionomitting the exhauster fan and its accompanying hood.

FIG. 2 is a perspective view similar to FIG. 1 but with the curb capremoved.

FIG. 3 is a perspective, exploded view of the structure shown in FIG. 2,the bafile assembly being viewed from its underside.

FIG. 4 is a further perspective view of the bafiie assembly showing itsunderside.

FIG. 5 is a perspective view of the base of the curb structure.

FIG. 6 is a schematic, cross-sectional view, on an en- 3,085,647Patented Apr. 16, 1963 larged scale of the curb structure shown in FIG.1 taken generally along the line 66 of FIG. 1 with a portion of a lowcontour type centrifugal exhaust fan being shown in place on thestructure.

Referring initially to FIGS. 1 and 5, the curb structure 10 is shown asincluding a sheet metal tube or box 11 having a preferably squarecross-sectional configuration. The base of the box 11 is provided withan outwardly inclined flange portion 12 which merges with a horizontallydisposed base plate 13. The base plate may be fabricated of sections toprovide mitered corners, the sections forming a central inlet aperture14.

The assembly is adapted to overlie an opening in the roof of a structureon which the curb is installed, with the inlet aperture 14 in the baseplate 13 registering with thereof opening. The marginal portions of thebase plate 13 extending beyond the inclined portion 12 may be suitablysealed to the adjacent building roof (not shown).

As may best be seen in FIG. 1, the box portion of the curb structurecarries a cap 15 whose outer margin is formed to provide a downwardlyturned flange 17 closely overlying the adjacent box 11 and securedthereto by any suitable means such as sheet metal screws 18. The centralportion of the cap is provided with a preferably square outlet openingbounded by an upturned flange 19. This flange 19 defines an outletopening 20 adapted to mount an exhaust fan assembly as will subsequentlybe pointed outwith reference to FIG. 6.

As may best be seen in FIG. 2, the cap structure 15 rests upon strips 21of a resilient sound absorbing ma terial such as sponge rubber overlyingthe inturned marginal upper edge of the box 11. The cap structure andthe exhaust fan carried thereby are further supported by four cornerassemblies indicated generally at 22 in FIG. 2. As may best be seen inFIG. 3, these corner assemblies comprise diagonally inwardly extendingstrips 23. The inner ends of the strips 23 are cut and bent outwardly soas to form tongues 24 which are rigidly secured to the sidewalls 26 of atray-shaped auxiliary baffle support 27. The upper marginal edges of thestrips 23 mount a preferably square primary baffle support plate 28provided with a preferably square central aperture 2 9 therethrough. Aswill be evident from FIGS. 3 and 4 the auxiliary baflle support member27 extends outwardly beyond the margins of the aperture 2 9 in the plate28.

The outer ends of the strips 23 are provided with flanges 31 whichextend at acute angles from the plane of the strips and parallel thesides of the box 11. Rigidly secured to the inner faces of each of theflanges 31 or integrally formed from the ends of the flanges 31 arebrackets 32 which are for-med to hook over the resilient material 21carried by the upper margin of :the box 11. The assembly is thussuspended, by means of the hooking brackets 32 from the upper margin ofthe box '11.

The outer ends of the strips 23 are further provided with diagonallyinwardly extending members 33 having a gusset portion 34 and ahorizontal flanged upper margin which is provided with an overlyingstrip of resilient material 36. As will be evident from comparing FIG. 2with FIG. 1 these inwardly extending members 33 underlie the diagonalcorner portions of the cap 15 and transfer the weight resting on the capto the corner portions of the box 11.

The structure so far described accommodates sound absorbing andattenuating material which may be of any suitable composition but hereinpreferably takes the form of slabs or sheets of fibreglass cut andshaped to the proper dimensions. The inner surfaces of the box 11 arelined with strips of acoustic material as indicated at 37 in FIG. 2. Thesheet 28 supports a primary baffle 38 of acoustic material, the primarybaffle being cut out as indicated at 39 in FIG. 2 so as to provide anaperture registering with the aperture 29 in the plate 28. It will beunderstood that apertures and 29 are preferably coaxial with the inletand outlet openings 14 and 29 respectively in the complete assembly,however, they might be offset sidewardly therefrom an might also bediscontinuous, that is, their total area might be made up of two or morecomponent apertures. The tray-shaped member 27 receives a slab ofacoustic material which provides an auxiliary bafile for the opening 29,this auxiliary baffle being indicated at 41 in FIG. 6. The portion ofthe base plate 13 which lies inboard of the vertical walls of the box 11is also provided with acoustic material to form a baffle 42.

Referring to FIG. 6, the operation of the structure just described willnow be set out. FIG. 6 is a schematic illustration of the structure ofFIGS. 1-5 and includes a portion of an exhaust fan assembly 43 mountedon the cap 15. The exhaust fan assembly includes a base portion 44having a depending flange 46 which closely overlies the flange 19 on thecap 15. Attached to the portion 44 is a section 47 which encircles thelower portion of a conventional centrifugal blower wheel indicatedgenerally at 43. It will be understood that the section 47 supports theblower wheel, a drive motor therefor and a cover member (not shown).With the exhaust fan in operation, air will be drawn through the inletopening 14 and will generally follow the paths indicated by arrows inFIG. 6 to be discharged through the curb structure. Air will flow aroundthe auxiliary baffie 41 and through the central aperture 39 in thebaffie 38. Air will also flow around the outer margins of the baflle 38.The presence of the central aperture 39 in the bafiie 38 and theauxiliary bafile 43 which shields the aperture 39 reduces the pressureloss in the curb structure from the loss which would occur if the bafiie38 were not provided with central air passage. The auxiliary bafile 41acts as an acoustic block for the aperture 39.

It should be noted that the corner assemblies which are suspended fromthe upper margin of the box 11 serve not only to support the bafiles 38and 41 in proper, spaced relation, but by means of the gusset sections33 serve to transfer the weight of the exhaust fan assembly to thecorner areas of the curb structure.

While the invention has been disclosed and described in some detail inthe drawings and foregoing description, they are to be considered asillustrative and not restrictive in character, as other modificationsmay readily suggest themselves to persons skilled in this art and withinthe broad scope of the invention, reference being had to the appendedclaims.

What is claimed is:

1. A curb structure for supporting an exhaust fan assembly comprising abase plate having a central inlet aperture therein, a tubular bodyportion extending vertically from said base plate and encircling saidinlet aperture, said body portion being square in cross-section, abaffie support assembly, elements carried by said baffle supportassembly and engaging the upper margin of said body portion whereby saidassembly is suspended within said body portion, said baffle supportassembly including upper and lower elements each extending diagonallyinwardly from the corners of said body portion, a primarysound-attenuating bafile supported on said lower elements in a positionoverlying said inlet aperture with its margins spaced from said bodyportion, said primary baflie having a central aperture therein coaxialwith said inlet aperture, an auxiliary sound-attenuating bafflesupported by said lower elements between said primary 'baffie and saidinlet aperture, said Iauxiliary baffle being disposed generally parallelto said primary bafiie and extending outwardly beyond the margins ofsaid central aperture in the primary baffle, and a cap member adapted tohave mounted thereon an exhaust fan assembly, said cap member overlyingthe upper end of said body portion and supported by said upper elementsof the bafiie support assembly, said upper elements serving to transferthe weight carried by said cap member to the corner areas of said bodyportion and said auxiliary baflle serving to acoustically shield thecentral aperture in said primary baffle.

2. A curb structure for supporting an exhaust fan assembly comprising abase plate having a central inlet aperture therein, a tubular bodyportion extending vertically from said base plate and encircling saidinlet aperture, said body portion being square in cross-section, abafiie support assembly disposed within said body portion, said bafflesupport assembly including upper and lower elements each extendingdiagonally inwardly from the corners of said body portion, a primarysound-attenuating bafile supported on said lower elements in a positionoverlying said inlet aperture with its margins spaced from said bodyportion, said primary b-afiie having a central aperture therein coaxialwith said inlet aperture, an auxiliary sound-attenuating bafflesupported by said lower elements between said primary baflle and saidinlet aperture, said auxiliary baffle being disposed generally parallelto said primary baflle and extending outwardly beyond the margins ofsaid central aperture in the primary bafiie, and a cap member adapted tohave mounted thereon an exhaust fan assembly, said cap member overlyingthe upper end of said body portion and supported by said upper elementsof the b allie support assembly, said upper elements serving to transferthe weight carried by said cap member to the corner areas of said bodyportion and said auxiliary baflle serving to acoustically shield thecentral aperture in said primary baffie.

3. A curb structure for supporting an exhaust fan assembly comprising abase plate having a central inlet aperture therein, a tubular bodyportion extending vertically from said base plate and encircling saidinlet aperture, said body portion being square in cross-section, a bafiie support assembly disposed within said body portion, said 'bafilesupport assembly including element extending diagonally inwardly fromthe corners of said body portion, a primary sound-attenuating bafllesupported on said elements in a position overlying said inlet aperturewith its margins spaced from said body portion, said primary battlehaving at least one aperture therein, an auxiliary soundattenuatingbafile supported by said elements between said primary baffle and saidinlet aperture, said auxiliary baifie being disposed generallly parallelto said primary 'bafile and extending outwardly beyond the margins ofsaid aperture in the primary baffle, and a cap member adapted to havemounted thereon an exhaust fan assembly, said auxiliary baffie servingto acoustically shield the aperture in said primary bafiie.

4. A curb structure for supporting an exhaust fan assembly comprising atubular body portion one end of which defines an inlet aperture, saidbody portion being square in cross-section, a bafiie support assemblydisposed within said body portion, said baffle support assemblyincluding elements extending diagonally inwardly from the corners ofsaid body portion, a primary sound-attenuating bafiie supported on saidelements in a position overlying said inlet aperture with its marginsspaced from said body portion, said primary baffle having at least oneaperture therein, an auxiliary sound-attenuating baflie supported bysaid elements between said primary baffle and said inlet aperture, saidauxiliary baffle being disposed generally parallel to said primarybaffle and extending outwardly beyond the margins of said aperture inthe primary baffle, said auxiliary baflle serving to acoustically shieldthe aperture in said primary baffle.

5. A curb structure for supporting an exhaust fan assembly comprising atubular body portion one end of which defines an inlet aperture, abafile support assembly disposed within said body portion, said bafflesupport assembly including elements extending generally radiallyinwardly from the inner surface of said body portion, a primarysound-attenuating baflle supported on said elements in a positionoverlying said inlet aperture with its margins spaced from said bodyportion, said primary baffle having at least one aperture therein, anauxiliary sound-attenuating bafl'le supported by said elements betweensaid primary baflie and said inlet aperture, said auxiliary bafile beingdisposed generally parallel to said primary bafile and extendingoutwardly beyond the margins of said aperture in the primary bafile,said auxiliary baffle serving to acoustically shield the aperture insaid primary bafiie.

6. A sound-attenuating structure for supporting a power driven airmoving device, said structure including a body portion providing axiallyaligned inlet and outlet apertures, a primary sound-attenuating bafflemounted within said body portion to overlie said inlet aperture andhaving its margins spaced from said body portion, at least one aperturein said primary baffle, and an auxiliary bafile disposed within saidbody portion between said primary bafiie and said inlet aperture andextending outwardly beyond the margins of said aperture in the primarybafi'le to acoustically shield said primary baffle aperture.

References Cited in the file of this patent UNITED STATES PATENTS1,289,856 Maxim Dec. 31, 1918 2,576,860 Shapiro Nov. 27, 1951 2,644,389Dauphinee July 7, 1953 2,750,865 Tutt June 19, 1956 2,875,678 ShepherdMar. 3, 1959 FOREIGN PATENTS 780,718 Great Britain Aug. 7, 1957

6. A SOUND-ATTENUATING STRUCTURE FOR SUPPORTING A POWER DRIVEN AIRMOVING DEVICE, SAID STRUCTURE INCLUDING A BODY PORTION PROVIDING AXIALLYALIGNED INLET AND OUTLET APERTURES, A PRIMARY SOUND-ATTENUATING BAFFLEMOUNTED WITHIN SAID BODY PORTION TO OVERLIE SAID INLET APERTURE ANDHAVING ITS MARGINS SPACED FROM SAID BODY PORTION, AT LEAST ONE APERTUREIN SAID PRIMARY BAFFLE AND AN AUXILIARY BAFFLE DISPOSED WITHIN SAID BODYPORTION BETWEEN SAID PRIMARY BAFFLE AND SAID INLET APERTURE ANDEXTENDING OUTWARDLY